[PATCH v2 0/6] MIPS: NT_PRFPREG regset handling fixes

[Maciej W. Rozycki]

Hi,

 This series corrects a number of issues with NT_PRFPREG regset, most 
importantly an FCSR access API regression introduced with the addition of 
MSA support, and then a few smaller issues with the get/set handlers.

 I have decided to factor out non-MSA and MSA context helpers as the first 
step to avoid the issue with excessive indentation that would inevitably 
happen if the regression fix was applied to current code as it stands.  
It shouldn't be a big deal with backporting as this code hasn't changed 
much since the regression, and it will make any future bacports easier.  
Only a call to `init_fp_ctx' will have to be trivially resolved (though 
arguably commit ac9ad83bc318 ("MIPS: prevent FP context set via ptrace 
being discarded"), which has added `init_fp_ctx', would be good to 
backport as far as possible instead).

 These changes have been verified by examining the register state recorded 
in core dumps manually with GDB, as well as by running the GDB test suite.  
No user of ptrace(2) PTRACE_GETREGSET and PTRACE_SETREGSET requests is 
known for the MIPS port, so this part remains not covered, however it is 
assumed to remain consistent with how the creation of core file works.

 See individual patch descriptions for further details, and for changes 
made since v1 to address concerns raised in the review.

  Maciej